Douglas Tucker - Academia.edu (original) (raw)
Papers by Douglas Tucker
Icarus, 2018
In the current model of early Solar System evolution, the stable members of the Jovian and Neptun... more In the current model of early Solar System evolution, the stable members of the Jovian and Neptunian Trojan populations were captured into resonance from the leftover reservoir of planetesimals during the outward migration of the giant planets. As a result, both Jovian and Neptunian Trojans share a common origin with the primordial disk population, whose other surviving members constitute today's trans-Neptunian object (TNO) populations. The cold (low inclination and small eccentricity) classical TNOs are ultra-red, while the dynamically excited "hot" (high inclination and larger eccentricity) population of TNOs contains a mixture of ultra-red and blue objects. In contrast, Jovian and Neptunian Trojans are observed to be blue. While the absence of ultra-red Jovian Trojans can be readily explained by the sublimation of volatile material from their surfaces due to the high flux of solar radiation at 5 AU, the lack of ultra-red Neptunian Trojans presents both a puzzle and a challenge to formation models. In this work we report the discovery by the Dark Energy Survey (DES) of two new dynamically stable L4 Neptunian Trojans, 2013 VX 30 and 2014 UU 240 , both with inclinations i > 30 • , making them the highest-inclination known stable Neptunian Trojans. We have measured the colors of these and three other dynamically stable Neptunian Trojans previously observed by DES, and find that 2013 VX 30 is ultra-red, the first such Neptunian Trojan in its class. As such, 2013 VX 30 may be a "missing link" between the Trojan and TNO populations. Using a simulation of the DES TNO detection efficiency, we find that there are 162 ± 73 Trojans with H r < 10 at the L4 Lagrange point of Neptune. Moreover, the blue-to-red Neptunian Trojan population ratio should be higher than 17:1. Based on this result, we discuss the possible origin of the ultra-red Neptunian Trojan population and its implications for the formation history of Neptunian Trojans.
AIP Conference Proceedings, 2003
The Sloan Digital Sky Survey (SDSS) will image one quarter of the sky centered on the northern ga... more The Sloan Digital Sky Survey (SDSS) will image one quarter of the sky centered on the northern galactic cap and produce a 3-D map of galaxies and quasars found in the sample. An additional 225 deg 2 southern survey will be imaged repeatedly on varying timescales. Here we discuss both archival searches in the SDSS catalog (such as SDSS J24602.54+011318.8) and active searches with the SDSS instruments (such as for GRB 010222) for GRB afterglows and other transient objects.
![Research paper thumbnail of The Two-Dimensional Power Spectrum of the Las Campanas Redshift Survey: Detection of Excess Power on 100 [ITAL]h[/ITAL][TSUP]−1[/TSUP] Mpc Scales](https://attachments.academia-assets.com/112544889/thumbnails/1.jpg)
](The Astrophysical Journal, 1996
We have measured the two-dimensional power spectrum of the Las Campanas Redshift Survey on scales... more We have measured the two-dimensional power spectrum of the Las Campanas Redshift Survey on scales between 30 and 200 h Ϫ1 Mpc (q 0 ϭ 0.5, H 0 ϭ 100 h km s Ϫ1 Mpc Ϫ1). Such an analysis is more sensitive to structure on scales greater than 50 h Ϫ1 Mpc than a full three-dimensional analysis, given the geometry of the survey. We find a strong peak in the power spectrum at 1100 h Ϫ1 Mpc relative to the smooth continuum expected from the best-fit cold dark matter model (Prob 1 2.5 ϫ 10 Ϫ4 with ⍀h ϭ 0.3 assuming a Gaussian random field). This signal is detected in two independent directions on the sky and has been identified with numerous structures visible in the survey that appear as walls and voids. Therefore, we conclude that there exists a significant increase in power on this scale and that such structures are common features in the local universe, z Յ 0.2.
Proceedings of the International Astronomical Union, 2012
SPIE Proceedings, 2014
The Dark Energy Survey (DES) is a next generation optical survey aimed at understanding the accel... more The Dark Energy Survey (DES) is a next generation optical survey aimed at understanding the accelerating expansion of the universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform the 5000 sq-degree wide field and 30 sq-degree supernova surveys, the DES Collaboration built the Dark Energy Camera (DECam), a 3 square-degree, 570-Megapixel CCD camera that was installed at the prime focus of the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO). DES started its first observing season on August 31, 2013 and observed for 105 nights through mid-February 2014. This paper describes DES "Year 1" (Y1), the strategy and goals for the first year's data, provides an outline of the operations procedures, lists the efficiency of survey operations and the causes of lost observing time, provides details about the quality of the first year's data, and hints at the "Year 2" plan and outlook.
(DES) is a current project in Fermilab's Cosmic Frontier. The DES is a 5000-squaredegree optical/... more (DES) is a current project in Fermilab's Cosmic Frontier. The DES is a 5000-squaredegree optical/near infrared imaging survey conducted over 5 years (2013-2018) for purposes of quantifying the properties of dark energy. Synthetic photometry of purehydrogen-atmosphere ("DA") white dwarfs is currently the preferred technique for determining the absolute zeropoint calibration of large sky surveys. For absolute calibration of the DES we seek to develop a "Golden Sample" of 30-100 DA white dwarfs. The starting point is a photometric and spectroscopic observational campaign of ≈ 1000 candidate white dwarfs in the DES footprint. Analysing imaging and spectroscopic data will allow us to narrow down this sample. We present results of the analysis of the observing effort. Over 50% of the observed candidates are to date DA white dwarfs. This portion of the the project was performed as part of the Department of Energy Visiting Faculty Program conducted at the Fermi National Accelerator Laboratory.
(DES) is a current project in Fermilab's Cosmic Frontier program. It is a 5000-square-degree opti... more (DES) is a current project in Fermilab's Cosmic Frontier program. It is a 5000-square-degree optical/near infrared imaging survey conducted over five years (2013-2018) for purposes of constraining the properties of dark energy. Photometric calibration of the DES is approached as a two part process. First is the Global Relative photometry effort to tie the survey in a seamless manner across the footprint. The second part of the effort is the Absolute photometry program which will set the zeropoints for each of the survey filters (grizY). Synthetic photometry of pure-hydrogen-atmosphere "DA" white dwarfs is currently the preferred technique for absolute zeropoint calibration of large sky surveys. For absolute calibration of the DES we are developing a "Golden Sample" of 30-100 DA white dwarfs, drawn from an initial sample of nearly 1000 candidate white dwarfs in the DES footprint. First, a spectroscopic observational campaign is needed to begin this process to verify spectral types and obtain synthetic magnitudes. The synthetic magnitudes will then be used to determine the filter zeropoints.
Observatory Operations: Strategies, Processes, and Systems II, 2008
Astronomy is changing. Large projects, large collaborations, and large budgets are becoming the n... more Astronomy is changing. Large projects, large collaborations, and large budgets are becoming the norm. The Sloan Digital Sky Survey (SDSS) is one example of this new astronomy, and in operating the original survey, we put in place and learned many valuable operating principles. Scientists sometimes have the tendency to invent everything themselves but when budgets are large, deadlines are many, and both are tight, learning from others and applying it appropriately can make the difference between success and failure. We offer here our experiences well as our thoughts, opinions, and beliefs on what we learned in operating the SDSS.
SPIE Proceedings, 2008
In this paper we describe the Dark Energy Camera (DECam), which will be the primary instrument us... more In this paper we describe the Dark Energy Camera (DECam), which will be the primary instrument used in the Dark Energy Survey. DECam will be a 3 sq. deg. mosaic camera mounted at the prime focus of the Blanco 4m telescope at the Cerro-Tololo International Observatory (CTIO). It consists of a large mosaic CCD focal plane, a five element optical corrector, five filters (g,r,i,z,Y), a modern data acquisition and control system and the associated infrastructure for operation in the prime focus cage. The focal plane includes of 62 2K x 4K CCD modules (0.27''/pixel) arranged in a hexagon inscribed within the roughly 2.2 degree diameter field of view and 12 smaller 2K x 2K CCDs for guiding, focus and alignment. The CCDs will be 250 micron thick fully-depleted CCDs that have been developed at the Lawrence Berkeley National Laboratory (LBNL). Production of the CCDs and fabrication of the optics, mechanical structure, mechanisms, and control system for DECam are underway; delivery of the instrument to CTIO is scheduled for 2010.
The Astronomical Journal, 2006
We report improved transformation equations between the u ′ g ′ r ′ i ′ z ′ and UBV R C I C photo... more We report improved transformation equations between the u ′ g ′ r ′ i ′ z ′ and UBV R C I C photometric systems. Although the details of the transformations depend on luminosity class, we find a typical rms scatter on the order of 0.001 magnitude if the sample is limited to main sequence stars. Furthermore, we find an accurate transformation requires complex, multi-color dependencies for the bluer bandpasses. Results for giant stars will be reported in a subsequent paper.
Publications of the Astronomical Society of the Pacific, 2000
Based on observations obtained with the Sloan Digital Sky Survey, which is owned and operated by ... more Based on observations obtained with the Sloan Digital Sky Survey, which is owned and operated by the Astrophysical Research Consortium. 2 Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin,
Publications of the Astronomical Society of the Pacific, 2013
PreCam, a precursor observational campaign supporting the Dark Energy Survey (DES), is designed t... more PreCam, a precursor observational campaign supporting the Dark Energy Survey (DES), is designed to produce a photometric and astrometric catalog of nearly a hundred thousand standard stars within the DES footprint, while the PreCam instrument also serves as a prototype testbed for the Dark Energy Camera (DECam)'s hardware and software. This catalog represents a potential 100-fold increase in Southern Hemisphere photometric standard stars, and therefore will be an important component in the calibration of the Dark Energy Survey. We provide details on the PreCam instrument's design, construction and testing, as well as results from a subset of the 51 nights of PreCam survey observations on the University of Michigan Department of Astronomy's Curtis-Schmidt telescope at Cerro Tololo Inter-American Observatory. We briefly describe the preliminary data processing pipeline that has been developed for PreCam data and the preliminary results of the instrument performance, as well as astrometry and photometry of a sample of stars previously included in other southern sky surveys.
Monthly Notices of the Royal Astronomical Society, 1997
We investigate properties of the correlation function of clusters of galaxies using geometrical m... more We investigate properties of the correlation function of clusters of galaxies using geometrical models. We show that the correlation function contains useful information on the geometry of the distribution of clusters. On small scales the correlation function depends on the shape and the size of superclusters. On large scales it describes the geometry of the distribution of superclusters. If superclusters are distributed randomly then the correlation function on large scales is featureless. If superclusters have a quasi-regular distribution then this regularity can be detected and measured by the correlation function. Superclusters of galaxies separated by large voids produce a correlation function with a minimum which corresponds to the mean separation between centres of superclusters and voids, followed by a secondary maximum corresponding to the distance between superclusters across voids. If superclusters and voids have a tendency to form a regular lattice then the correlation function on large scales has quasiregularly spaced maxima and minima of decaying amplitude; i.e. it is oscillating. The period of oscillations is equal to the step size of the grid of the lattice. We also calculate the power spectrum and the void diameter distribution for our models and compare the geometrical information of the correlation function with other statistics. We find that geometric properties (the regularity of the distribution of clusters on large scales) are better quantified by the correlation function. We also analyse errors in the correlation function and the power spectrum by generating random realizations of models and finding the scatter of these realizations.
Monthly Notices of the Royal Astronomical Society, 1997
We use rich clusters of galaxies in the Northern and Southern Galactic hemispheres up to a redshi... more We use rich clusters of galaxies in the Northern and Southern Galactic hemispheres up to a redshift z = 0.12 to determine the cluster correlation function for a separation interval =650h-1 Mpc (h is the Hubble constant in units of 100 kms-1Mpc-1). We show that superclusters of galaxies and voids between them form a moderately regular network. As a result the correlation function determined for clusters located in rich superclusters oscillates: it has a series of regularly spaced secondary maxima and minima. The scale of the superclustervoid network, determined from the period of oscillations, is P = 115 ± 15 h-1 Mpc. Five periods are observed. The correlation function found for clusters in poor and medium-rich superclusters is zero on large scales. The correlation functions calculated separately for the Northern and Southern Galactic hemispheres are similar; only the amplitude of oscillations for clusters in the Southern hemisphere is larger by a factor of about 1.5. We investigate the influence of possible errors in the correlation function. The amplitude of oscillations for clusters in very rich superclusters is about 3 times larger than the estimated error. We argue that the oscillations in the correlation function are due neither to the doublecone shape of the observed volume of space, nor to the inaccuracy in the selection function. 'We compare the observed cluster correlation function with similar functions derived for popular models of structure formation, as well as for simple geometrical models of cluster distribution. We find that the production of the observed cluster correlation function in any model with a smooth transition of the power spectrum from a Harrison-Zeldovich regime with positive spectral index at long wavelengths to a negative spectral index at short wavelengths is highly unlikely. The power spectrum must have an extra peak located at a wavelength equal to the period of oscillations of the correlation function. The relative amplitude of the peak over the smooth spectrum is probably of the order of a factor of at least 1.25. These quantitative tests show that high-density regions in the Universe marked by rich clusters of galaxies are distributed more regularly than expected. Thus our present understanding of structure formation needs revision.
Astronomical images taken from a telescope must go through "astronomical image processing" to rem... more Astronomical images taken from a telescope must go through "astronomical image processing" to remove instrumental signatures. The Dark Energy Survey (DES), which will start operations in 2012, will use a 570 megapixel Dark Energy Camera (DECam) to study the mystery of the acceleration of the expanding universe. The DECam will use DES filters and 74 of a new type of astronomical Charge Coupled Device (CCD) that is particularly efficient in detecting near-infrared light. Together, the DES filters and DECam CCDs are optimized for the measurement of redshifts of distant galaxies. In preparation for the DES, data were collected from the 1 meter telescope at Cerro Tololo Inter-American Observatory (CTIO) in Chile, using a DES filter set and a DECam CCD as a test set for the initial analysis of data. Here, these CTIO-1m data were used to determine the relationship between the apparent measured brightness of stars of known brightness (standard stars) and the amount of atmosphere the telescope looks through (angular distance from the zenith or "airmass"). This relationship was tested against the results from another telescope using similar filters. Finally, this relationship was used to calibrate the brightness of stars of unknown brightness that were also observed in the CTIO 1m data set.
Scientific Justification (will be made publicly available for accepted proposals): The Sloan Digi... more Scientific Justification (will be made publicly available for accepted proposals): The Sloan Digital Sky Survey (SDSS) has been obtaining engineering and commissioning imaging data for over a year and the survey is expected to get underway and generate science quality data in early 2000. Though the SDSS is geared to the northern hemisphere, as the survey photometric system (u g r i z) gains acceptance within the astronomical community, the need for southern standard stars will increase. To maintain continuity with the SDSS northern and equatorial standard stars we propose to develop of a series of southern standards with the u g r i z filters for use by the astronomical community. These southern standards will be developed using the same observers, reduction software and observing and selection procedures as the initial SDSS standard system.
The Dark Energy Survey Data Management (DESDM) system will process and archive the data from the ... more The Dark Energy Survey Data Management (DESDM) system will process and archive the data from the Dark Energy Survey (DES) over the five year period of operation. This paper focuses on a new adaptable processing framework developed to perform highly automated, high performance data parallel processing. The new processing framework has been used to process 45 nights of simulated DECam supernova imaging data, and was extensively used in the DES Data Challenge 4, where it was used to process thousands of square degrees of simulated DES data.
We calculate the luminosity function of galaxies of the Early Data Release of the Sloan Digital S... more We calculate the luminosity function of galaxies of the Early Data Release of the Sloan Digital Sky Survey (SDSS) and the Las Campanas Redshift Survey (LCRS). The luminosity function depends on redshift, density of the environment and is different for the Northern and Southern slice of SDSS. We use luminosity functions to derive the number and luminosity density fields of galaxies of the SDSS and LCRS surveys with a grid size of 1 h −1 Mpc for flat cosmological models with Ωm = 0.3 and ΩΛ = 0.7. We investigate the properties of these density fields, their dependence on parameters of the luminosity function and selection effects. We find that the luminosity function depends on the distance and the density of the environment. The last dependence is strong: in high-density regions brightest galaxies are more luminous than in low-density regions by a factor up to 5 (1.7 magnitudes).
Icarus, 2018
In the current model of early Solar System evolution, the stable members of the Jovian and Neptun... more In the current model of early Solar System evolution, the stable members of the Jovian and Neptunian Trojan populations were captured into resonance from the leftover reservoir of planetesimals during the outward migration of the giant planets. As a result, both Jovian and Neptunian Trojans share a common origin with the primordial disk population, whose other surviving members constitute today's trans-Neptunian object (TNO) populations. The cold (low inclination and small eccentricity) classical TNOs are ultra-red, while the dynamically excited "hot" (high inclination and larger eccentricity) population of TNOs contains a mixture of ultra-red and blue objects. In contrast, Jovian and Neptunian Trojans are observed to be blue. While the absence of ultra-red Jovian Trojans can be readily explained by the sublimation of volatile material from their surfaces due to the high flux of solar radiation at 5 AU, the lack of ultra-red Neptunian Trojans presents both a puzzle and a challenge to formation models. In this work we report the discovery by the Dark Energy Survey (DES) of two new dynamically stable L4 Neptunian Trojans, 2013 VX 30 and 2014 UU 240 , both with inclinations i > 30 • , making them the highest-inclination known stable Neptunian Trojans. We have measured the colors of these and three other dynamically stable Neptunian Trojans previously observed by DES, and find that 2013 VX 30 is ultra-red, the first such Neptunian Trojan in its class. As such, 2013 VX 30 may be a "missing link" between the Trojan and TNO populations. Using a simulation of the DES TNO detection efficiency, we find that there are 162 ± 73 Trojans with H r < 10 at the L4 Lagrange point of Neptune. Moreover, the blue-to-red Neptunian Trojan population ratio should be higher than 17:1. Based on this result, we discuss the possible origin of the ultra-red Neptunian Trojan population and its implications for the formation history of Neptunian Trojans.
AIP Conference Proceedings, 2003
The Sloan Digital Sky Survey (SDSS) will image one quarter of the sky centered on the northern ga... more The Sloan Digital Sky Survey (SDSS) will image one quarter of the sky centered on the northern galactic cap and produce a 3-D map of galaxies and quasars found in the sample. An additional 225 deg 2 southern survey will be imaged repeatedly on varying timescales. Here we discuss both archival searches in the SDSS catalog (such as SDSS J24602.54+011318.8) and active searches with the SDSS instruments (such as for GRB 010222) for GRB afterglows and other transient objects.
The Astrophysical Journal, 1996
We have measured the two-dimensional power spectrum of the Las Campanas Redshift Survey on scales... more We have measured the two-dimensional power spectrum of the Las Campanas Redshift Survey on scales between 30 and 200 h Ϫ1 Mpc (q 0 ϭ 0.5, H 0 ϭ 100 h km s Ϫ1 Mpc Ϫ1). Such an analysis is more sensitive to structure on scales greater than 50 h Ϫ1 Mpc than a full three-dimensional analysis, given the geometry of the survey. We find a strong peak in the power spectrum at 1100 h Ϫ1 Mpc relative to the smooth continuum expected from the best-fit cold dark matter model (Prob 1 2.5 ϫ 10 Ϫ4 with ⍀h ϭ 0.3 assuming a Gaussian random field). This signal is detected in two independent directions on the sky and has been identified with numerous structures visible in the survey that appear as walls and voids. Therefore, we conclude that there exists a significant increase in power on this scale and that such structures are common features in the local universe, z Յ 0.2.
Proceedings of the International Astronomical Union, 2012
SPIE Proceedings, 2014
The Dark Energy Survey (DES) is a next generation optical survey aimed at understanding the accel... more The Dark Energy Survey (DES) is a next generation optical survey aimed at understanding the accelerating expansion of the universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform the 5000 sq-degree wide field and 30 sq-degree supernova surveys, the DES Collaboration built the Dark Energy Camera (DECam), a 3 square-degree, 570-Megapixel CCD camera that was installed at the prime focus of the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO). DES started its first observing season on August 31, 2013 and observed for 105 nights through mid-February 2014. This paper describes DES "Year 1" (Y1), the strategy and goals for the first year's data, provides an outline of the operations procedures, lists the efficiency of survey operations and the causes of lost observing time, provides details about the quality of the first year's data, and hints at the "Year 2" plan and outlook.
(DES) is a current project in Fermilab's Cosmic Frontier. The DES is a 5000-squaredegree optical/... more (DES) is a current project in Fermilab's Cosmic Frontier. The DES is a 5000-squaredegree optical/near infrared imaging survey conducted over 5 years (2013-2018) for purposes of quantifying the properties of dark energy. Synthetic photometry of purehydrogen-atmosphere ("DA") white dwarfs is currently the preferred technique for determining the absolute zeropoint calibration of large sky surveys. For absolute calibration of the DES we seek to develop a "Golden Sample" of 30-100 DA white dwarfs. The starting point is a photometric and spectroscopic observational campaign of ≈ 1000 candidate white dwarfs in the DES footprint. Analysing imaging and spectroscopic data will allow us to narrow down this sample. We present results of the analysis of the observing effort. Over 50% of the observed candidates are to date DA white dwarfs. This portion of the the project was performed as part of the Department of Energy Visiting Faculty Program conducted at the Fermi National Accelerator Laboratory.
(DES) is a current project in Fermilab's Cosmic Frontier program. It is a 5000-square-degree opti... more (DES) is a current project in Fermilab's Cosmic Frontier program. It is a 5000-square-degree optical/near infrared imaging survey conducted over five years (2013-2018) for purposes of constraining the properties of dark energy. Photometric calibration of the DES is approached as a two part process. First is the Global Relative photometry effort to tie the survey in a seamless manner across the footprint. The second part of the effort is the Absolute photometry program which will set the zeropoints for each of the survey filters (grizY). Synthetic photometry of pure-hydrogen-atmosphere "DA" white dwarfs is currently the preferred technique for absolute zeropoint calibration of large sky surveys. For absolute calibration of the DES we are developing a "Golden Sample" of 30-100 DA white dwarfs, drawn from an initial sample of nearly 1000 candidate white dwarfs in the DES footprint. First, a spectroscopic observational campaign is needed to begin this process to verify spectral types and obtain synthetic magnitudes. The synthetic magnitudes will then be used to determine the filter zeropoints.
Observatory Operations: Strategies, Processes, and Systems II, 2008
Astronomy is changing. Large projects, large collaborations, and large budgets are becoming the n... more Astronomy is changing. Large projects, large collaborations, and large budgets are becoming the norm. The Sloan Digital Sky Survey (SDSS) is one example of this new astronomy, and in operating the original survey, we put in place and learned many valuable operating principles. Scientists sometimes have the tendency to invent everything themselves but when budgets are large, deadlines are many, and both are tight, learning from others and applying it appropriately can make the difference between success and failure. We offer here our experiences well as our thoughts, opinions, and beliefs on what we learned in operating the SDSS.
SPIE Proceedings, 2008
In this paper we describe the Dark Energy Camera (DECam), which will be the primary instrument us... more In this paper we describe the Dark Energy Camera (DECam), which will be the primary instrument used in the Dark Energy Survey. DECam will be a 3 sq. deg. mosaic camera mounted at the prime focus of the Blanco 4m telescope at the Cerro-Tololo International Observatory (CTIO). It consists of a large mosaic CCD focal plane, a five element optical corrector, five filters (g,r,i,z,Y), a modern data acquisition and control system and the associated infrastructure for operation in the prime focus cage. The focal plane includes of 62 2K x 4K CCD modules (0.27''/pixel) arranged in a hexagon inscribed within the roughly 2.2 degree diameter field of view and 12 smaller 2K x 2K CCDs for guiding, focus and alignment. The CCDs will be 250 micron thick fully-depleted CCDs that have been developed at the Lawrence Berkeley National Laboratory (LBNL). Production of the CCDs and fabrication of the optics, mechanical structure, mechanisms, and control system for DECam are underway; delivery of the instrument to CTIO is scheduled for 2010.
The Astronomical Journal, 2006
We report improved transformation equations between the u ′ g ′ r ′ i ′ z ′ and UBV R C I C photo... more We report improved transformation equations between the u ′ g ′ r ′ i ′ z ′ and UBV R C I C photometric systems. Although the details of the transformations depend on luminosity class, we find a typical rms scatter on the order of 0.001 magnitude if the sample is limited to main sequence stars. Furthermore, we find an accurate transformation requires complex, multi-color dependencies for the bluer bandpasses. Results for giant stars will be reported in a subsequent paper.
Publications of the Astronomical Society of the Pacific, 2000
Based on observations obtained with the Sloan Digital Sky Survey, which is owned and operated by ... more Based on observations obtained with the Sloan Digital Sky Survey, which is owned and operated by the Astrophysical Research Consortium. 2 Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin,
Publications of the Astronomical Society of the Pacific, 2013
PreCam, a precursor observational campaign supporting the Dark Energy Survey (DES), is designed t... more PreCam, a precursor observational campaign supporting the Dark Energy Survey (DES), is designed to produce a photometric and astrometric catalog of nearly a hundred thousand standard stars within the DES footprint, while the PreCam instrument also serves as a prototype testbed for the Dark Energy Camera (DECam)'s hardware and software. This catalog represents a potential 100-fold increase in Southern Hemisphere photometric standard stars, and therefore will be an important component in the calibration of the Dark Energy Survey. We provide details on the PreCam instrument's design, construction and testing, as well as results from a subset of the 51 nights of PreCam survey observations on the University of Michigan Department of Astronomy's Curtis-Schmidt telescope at Cerro Tololo Inter-American Observatory. We briefly describe the preliminary data processing pipeline that has been developed for PreCam data and the preliminary results of the instrument performance, as well as astrometry and photometry of a sample of stars previously included in other southern sky surveys.
Monthly Notices of the Royal Astronomical Society, 1997
We investigate properties of the correlation function of clusters of galaxies using geometrical m... more We investigate properties of the correlation function of clusters of galaxies using geometrical models. We show that the correlation function contains useful information on the geometry of the distribution of clusters. On small scales the correlation function depends on the shape and the size of superclusters. On large scales it describes the geometry of the distribution of superclusters. If superclusters are distributed randomly then the correlation function on large scales is featureless. If superclusters have a quasi-regular distribution then this regularity can be detected and measured by the correlation function. Superclusters of galaxies separated by large voids produce a correlation function with a minimum which corresponds to the mean separation between centres of superclusters and voids, followed by a secondary maximum corresponding to the distance between superclusters across voids. If superclusters and voids have a tendency to form a regular lattice then the correlation function on large scales has quasiregularly spaced maxima and minima of decaying amplitude; i.e. it is oscillating. The period of oscillations is equal to the step size of the grid of the lattice. We also calculate the power spectrum and the void diameter distribution for our models and compare the geometrical information of the correlation function with other statistics. We find that geometric properties (the regularity of the distribution of clusters on large scales) are better quantified by the correlation function. We also analyse errors in the correlation function and the power spectrum by generating random realizations of models and finding the scatter of these realizations.
Monthly Notices of the Royal Astronomical Society, 1997
We use rich clusters of galaxies in the Northern and Southern Galactic hemispheres up to a redshi... more We use rich clusters of galaxies in the Northern and Southern Galactic hemispheres up to a redshift z = 0.12 to determine the cluster correlation function for a separation interval =650h-1 Mpc (h is the Hubble constant in units of 100 kms-1Mpc-1). We show that superclusters of galaxies and voids between them form a moderately regular network. As a result the correlation function determined for clusters located in rich superclusters oscillates: it has a series of regularly spaced secondary maxima and minima. The scale of the superclustervoid network, determined from the period of oscillations, is P = 115 ± 15 h-1 Mpc. Five periods are observed. The correlation function found for clusters in poor and medium-rich superclusters is zero on large scales. The correlation functions calculated separately for the Northern and Southern Galactic hemispheres are similar; only the amplitude of oscillations for clusters in the Southern hemisphere is larger by a factor of about 1.5. We investigate the influence of possible errors in the correlation function. The amplitude of oscillations for clusters in very rich superclusters is about 3 times larger than the estimated error. We argue that the oscillations in the correlation function are due neither to the doublecone shape of the observed volume of space, nor to the inaccuracy in the selection function. 'We compare the observed cluster correlation function with similar functions derived for popular models of structure formation, as well as for simple geometrical models of cluster distribution. We find that the production of the observed cluster correlation function in any model with a smooth transition of the power spectrum from a Harrison-Zeldovich regime with positive spectral index at long wavelengths to a negative spectral index at short wavelengths is highly unlikely. The power spectrum must have an extra peak located at a wavelength equal to the period of oscillations of the correlation function. The relative amplitude of the peak over the smooth spectrum is probably of the order of a factor of at least 1.25. These quantitative tests show that high-density regions in the Universe marked by rich clusters of galaxies are distributed more regularly than expected. Thus our present understanding of structure formation needs revision.
Astronomical images taken from a telescope must go through "astronomical image processing" to rem... more Astronomical images taken from a telescope must go through "astronomical image processing" to remove instrumental signatures. The Dark Energy Survey (DES), which will start operations in 2012, will use a 570 megapixel Dark Energy Camera (DECam) to study the mystery of the acceleration of the expanding universe. The DECam will use DES filters and 74 of a new type of astronomical Charge Coupled Device (CCD) that is particularly efficient in detecting near-infrared light. Together, the DES filters and DECam CCDs are optimized for the measurement of redshifts of distant galaxies. In preparation for the DES, data were collected from the 1 meter telescope at Cerro Tololo Inter-American Observatory (CTIO) in Chile, using a DES filter set and a DECam CCD as a test set for the initial analysis of data. Here, these CTIO-1m data were used to determine the relationship between the apparent measured brightness of stars of known brightness (standard stars) and the amount of atmosphere the telescope looks through (angular distance from the zenith or "airmass"). This relationship was tested against the results from another telescope using similar filters. Finally, this relationship was used to calibrate the brightness of stars of unknown brightness that were also observed in the CTIO 1m data set.
Scientific Justification (will be made publicly available for accepted proposals): The Sloan Digi... more Scientific Justification (will be made publicly available for accepted proposals): The Sloan Digital Sky Survey (SDSS) has been obtaining engineering and commissioning imaging data for over a year and the survey is expected to get underway and generate science quality data in early 2000. Though the SDSS is geared to the northern hemisphere, as the survey photometric system (u g r i z) gains acceptance within the astronomical community, the need for southern standard stars will increase. To maintain continuity with the SDSS northern and equatorial standard stars we propose to develop of a series of southern standards with the u g r i z filters for use by the astronomical community. These southern standards will be developed using the same observers, reduction software and observing and selection procedures as the initial SDSS standard system.
The Dark Energy Survey Data Management (DESDM) system will process and archive the data from the ... more The Dark Energy Survey Data Management (DESDM) system will process and archive the data from the Dark Energy Survey (DES) over the five year period of operation. This paper focuses on a new adaptable processing framework developed to perform highly automated, high performance data parallel processing. The new processing framework has been used to process 45 nights of simulated DECam supernova imaging data, and was extensively used in the DES Data Challenge 4, where it was used to process thousands of square degrees of simulated DES data.
We calculate the luminosity function of galaxies of the Early Data Release of the Sloan Digital S... more We calculate the luminosity function of galaxies of the Early Data Release of the Sloan Digital Sky Survey (SDSS) and the Las Campanas Redshift Survey (LCRS). The luminosity function depends on redshift, density of the environment and is different for the Northern and Southern slice of SDSS. We use luminosity functions to derive the number and luminosity density fields of galaxies of the SDSS and LCRS surveys with a grid size of 1 h −1 Mpc for flat cosmological models with Ωm = 0.3 and ΩΛ = 0.7. We investigate the properties of these density fields, their dependence on parameters of the luminosity function and selection effects. We find that the luminosity function depends on the distance and the density of the environment. The last dependence is strong: in high-density regions brightest galaxies are more luminous than in low-density regions by a factor up to 5 (1.7 magnitudes).